Table 2.

Science is characterised by the quantitative expression of likelihood. Yet, deductive reasoning is essentially qualitative. This table—used by the Intergovernmental Panel on Climate Change (IPCC) [43]—is a useful bridge between the qualitative and quantitative (Section 4.4).

Qualitative Expression	Quantitative Expression
Virtually certain	99–100% probability
Extremely likely	95–100% probability
Very likely	90–100% probability
Likely	66–100% probability
About as likely as not	33–66% probability
Unlikely	0–33% probability
Very unlikely	0–10% probability
Extremely unlikely	0–5% probability
Exceptionally unlikely	0–1% probability